The Medial Sural Artery Perforator Flap: A Historical Trek from Ignominious to "Workhorse"

Abstract

Rather than just another "review," this is intended to be an "overview" of the entire subject of the medial sural artery perforator (MSAP) flap as has been presented in the reconstructive literature from its inception in 2001 until the present, with any exceptions not purposefully overlooked. Unfortunately, the pertinent anatomy of the MSAP flap is always anomalous like most other perforator flaps, and perhaps even more variable. No schematic exists to facilitate the identification of a dominant musculocutaneous perforator about which to design the flap, so some adjunctive technology may be highly valuable for this task. However, if a relatively thin free flap is desirable for a small or moderate sized defect that requires a long pedicle with larger caliber vessels, the MSAP flap deserves consideration. Indeed, for many, this has replaced the radial forearm flap such as for partial tongue reconstruction. Most consider the donor site deformity, even if only a conspicuous scar on the calf, to be a contraindication. Yet certainly if used as a local flap for the knee, popliteal fossa, or proximal leg, or as a free flap for the ipsilateral lower extremity where a significant recipient site deformity already exists, can anyone really object that this is not a legitimate indication? As with any perforator flap, advantages and disadvantages exist, which must be carefully perused before a decision to use the MSAP flap is made. Perhaps not a "workhorse" flap for general use throughout the body, the MSAP flap in general may often be a valuable alternative.

Keywords: MSAP flap; calf flap; lower extremity; medial sural artery perforator flap.

Fig. 1

Classification and frequency (%) of branching patterns of the medial sural artery according to Dusseldorp et al. Type I: single branch (31%). Type IIa: dual branches with takeoff superior to tibial plateau (35%). Type IIb: dual branches with takeoff inferior to tibial plateau (24%). Type III: three or more branches, all with takeoff superior to the tibial plateau (10%).

Fig. 2

Existing schematics intended to facilitate the preoperative identification of the location of a medial sural artery perforator (see text for details): Kim et al : within hemi-circle 8 cm below the popliteal crease (PC) on line drawn from midpoint of PC to prominence of the medial malleolus (MM). Song et al : search begins at midpoint of line of Kim; Thione et al : found ± 1.0 cm from the vertical midline of the medial gastrocnemius muscle (MGM); Choi et al : inside the triangle formed by the extent of the MGM between lines from the midpoint of the PC to the Achilles tendon and the medial calcaneus; Wang et al : within the circle centered at the intersection of line from the medial epicondyle of the femur to the prominence of the lateral malleolus with the line of Kim; Kao et al : region encompassed superiorly by the PC, line from the midpoint of the PC to the Achilles tendon, the distal border of the MGM, and the fourth line from the medial tibial condyle to the prominence of the MM.

Fig. 3

( A ) Failed right ankle pilon fracture reduction, with open lateral malleolus wound extending into ankle joint. ( B ) Using a thermography camera, the second “hotspot” seen marked on the medial calf as was the spot “X” above. ( C ) Medial sural artery perforator (MSAP) flap designed on the medial calf to potentially include both perforator sites “X” as determined by thermography. ( D ) Chimeric MSAP flap in situ, with perforators ( P ) found exactly at predicted points “X,” vascular clamp on the greater saphenous vein branch (V) available for supercharging, course of the medial sural artery superficial intramuscular source branch (proximal yellow arrow), continuation of this branch ( distal yellow arrow ) past the second perforator origin to independently supply a small portion of the medial gastrocnemius muscle (MG) that will be inset into the cavity entering the ankle joint, harvest site of the MG ( black arrow ), rent through the MG for pedicle harvest (inferior to dotted line ). ( E ) Free chimeric MSAP flap, predicted perforator sites “X” ( black arrows ) corresponded to their actual location ( P [yellow arrows follow course of medial sural pedicle]). ( F ) Right lateral ankle status 5 weeks posttransfer prior to fusion. ( G ) Typical final calf donor site scar.

Fig. 4

“Pinch test” donor site comparison in another individual with deep inferior epigastric perforator (DIEP), anterolateral thigh (ALT), and medial sural artery perforator (MSAP)—proving typically to be the thinnest.

Fig. 5

This medial sural artery perforator (MSAP) flap thickness as measured in situ was 2.0 cm. The same flap used for Fig. 3 was used here.

Fig. 6

The medial sural artery perforator (MSAP) free flap for resurfacing the lower lip provided coverage, but obliterated subunit contour with a color differential from the rest of the face that would be aesthetically unacceptable.